Generally, a stapler comprises a driver unit which contains a number of staples and ejects a C-shaped staple toward sheets of paper by a driver, and a clincher unit which is opposed to the driver unit and clinches tip end of the leg of the staple penetrated through the sheets of paper along a back face of the sheets of paper. The staple is ejected from the driver unit toward the sheets of paper placed between the two units, and a clincher device of the clincher unit engages with the tip end of the leg of the staple penetrated through the sheets of paper to inwardly bend the leg so as to clinch the leg along the back face of the sheets of paper.
It is required that the driver unit and the clincher unit are positioned in accurate alignment so that a leading end of the staple ejected from the driver unit can be accurately engaged with the clincher device of the clincher unit. However, in the stapler mounted in a copying machine or the like, the driver unit and the clincher unit are constructed separately, and the two units are independently controlled so as to move in a sliding direction and in a rotary direction in order that the sheets of paper after copied can be bound at a desired position. Because the stapler is so constructed that the two units can move in this manner, a positional deviation may occur between the staple ejected from the driver unit and the clincher device of the clincher unit, and so, the leg of the staple ejected from the driver unit may not be engaged with the clincher device of the clincher unit, which will cause a binding error. Therefore, there has been such a problem that it takes a long time to adjust positioning of the two units.
Moreover, the conventional clincher device of the stapler is so constructed that a receiving face for the leg of the staple is wide, and stationary walls are provided so as to be opposed to each other on both sides of a clincher member with clinching groove having a substantially same width as the staple. In the stationary walls, an inclined face for guiding the tip end of the leg of the staple which have penetrated through the sheets of paper into the clinching groove of the clincher member is formed, and the tip end of the leg of the staple which have penetrated through the sheets of paper is guided into the clinching groove of the clincher member along the inclined face (Refer to JP-Y-06-007893, for example).
As shown in FIG. 8, since the receiving face is formed wide in the above conventional clincher device 20, leg portion S1 of a staple S can be engaged with the clincher device 20, even in case where a slight deviation has occurred between the clincher unit and the driver unit. However, since the staple leg S1 is guided into clinching groove 23 of a clincher member 22 along inclined face 21, when a tip end S2 of the staple leg S1 penetrated through sheets of paper is inwardly bent by the clincher member 22, the staple S will be inclined and fallen down while the tip end S2 of the staple leg S1 is guided in a longitudinal direction by the inclined face 21. As the results, such a phenomenon that the sheets of paper is bound in a state where both the legs S1 are not in parallel with a crown part of the staple but inclined, as shown in FIG. 9, may occur. In case where the staple S having the long leg S1 is used, it may sometimes happen that both the legs S1 are crossed.